Four years ago, New York's Department of Environmental Conservation and Department of Health issued new guidance on soil vapour intrusion, which triggered the ongoing re-evaluation of over 400 contaminated sites and the re-openings of dozens of sites for new testing or mitigation. The US Environmental Protection Agency (EPA) is now taking the first steps towards revising its own vapour intrusion guidance.

On August 30 2010 the EPA's Office of Solid Waste and Emergency Response released its review of the Draft 2002 Subsurface Vapour Intrusion Guidance. The review highlights areas of existing guidance that the EPA plans to update or change over the next two years.

In 2002 the EPA released draft guidance for detecting and responding to vapour intrusion, caused by the migration of subsurface contamination into overlying buildings. Vapour intrusion is most commonly found at sites with elevated levels of volatile organic compounds – including chlorinated solvents and gasoline – in the soil or groundwater.

In response to recent scientific developments, last year the EPA inspector general recommended that the agency update and finalise its guidance, which remains in draft form. The EPA hopes to complete that process by November 2012, and the recent review highlights various assumptions and methodologies that are subject to change. For instance, the EPA plans to:

  • incorporate multiple lines of evidence into vapour intrusion screening determinations;
  • expand its guidance related to non-residential and yet-to-be-constructed buildings; and
  • provide for the collection of indoor air samples earlier in the investigation process.

The EPA intends to solicit public comment and hold hearings on the guidance revisions in 2011. The EPA asserts that it is not required to take comment on guidance documents, but often does so for higher-profile issues.

Meanwhile, New York continues its process of re-evaluating contaminated sites for vapour intrusion pathways, including many properties that had previously been remediated and de-listed. Purchasers and lenders also increasingly investigate vapour intrusion as part of their Phase 1 environmental site assessments.

Thus far, the EPA has not announced plans to re-open Superfund sites to investigate vapour intrusion. However, where low levels of contamination are left at a remediated site, the Superfund statute requires a site review every five years, at which point additional work may be needed to address vapour intrusion threats based on new guidance.

For further information on this topic please contact Christine Leas, Jeffrey Gracer or Michael Bogin at Sive Paget & Riesel PC by telephone (+1 212 421 2150), fax (+1 212 421 2035) or email (, or

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